Green light-emitting material is widely applied in our daily life. For example, a green light-emitting material CeMgAl11O19:Tb which converts the ultraviolet ray of 254 nm emitted by mercury vapor into a green visible light for emission is used in the fluorescent lamp. ZnS:Cu,Au,Al is utilized in the color picture tube of the television to convert the cathode ray into a green visible light for emission. For the X-ray imaging system widely used in the medical field, the imaging is achieved by the excitation of the X-ray passing through the human body on the green light-emitting material Gd2O2S:Tb and used for assisting a doctor in making a diagnosis of a patient's condition. It can be seen from this that it is needed to select different green light-emitting materials in different application fields. However, there is still no kind of green light-emitting material which can possess excellent photoluminescence, cathodoluminescence and X-radioluminescence properties simultaneously up to now.
Furthermore, all these light-emitting materials above are non-transparent powders and consequently have poor transparence. It is required for these powders to be ground and washed before screen coating and to be heat treated necessarily after screen coating. Besides, there is certain requirement on the particle size of the powder. The entire process can cause the luminescent property of the material to be reduced.